The project is the second phase of a major undertaking to redesign Route 110 -- one of Long Island's major business corridors -- between the Northern State and the Long Island Expressway.
The first phase, a $28-million reconstruction of the Route 110 bridge over the LIE financed by state and federal aid, is expected to be complete this summer, DOT spokeswoman Eileen Peters said.
The Northern State bridge, constructed under the master planner Robert Moses in 1948, is considered deficient and "structurally obsolete," according to DOT bridge inspection data.
Though safe to drive on, Peters said, "It's really not serving the 120,000 motorists who pass under and over every single day."
The redesigned bridge and interchange will include safer, longer entrance and exit ramps; continuous shoulders for bicyclists; and sidewalks, crosswalks and countdown signals for pedestrians, she said.
There are now no accommodations for pedestrians or bicyclists passing under the bridge.
A redesigned stretch of Route 110, between Arlington Street, south of the parkway, and Fletcher Place, to the north, will have three lanes in each direction and space for buses to pull over at bus stops.
The Northern State project is scheduled to be complete in the winter of 2013-2014. It is to be followed by a third phase, extending the improvements south on Route 110 to the LIE.
Peters said the project has earned a high rating for environmental sensitivity, and will include improved drainage systems, tree plantings and the reuse of topsoil and timber.
The contractor, Grace Industries of Plainview, will reuse granite from the existing bridge for the new structure, preserving "the historical character of the bridge," Peters said.
Lane closures will occur only at night, she said.
Lawmakers praised the project, saying it would improve access to a vital business district, and support the relocation of Canon's Western Hemisphere international headquarters to Melville.
Assemb. James Conte (R-Huntington Station) called it "a long-awaited infrastructural need of this region."